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In 2005 Professor Mike Brown and his team discovered a new dwarf planet at the edge of our solar system. He spotted Eris in the Kuiper belt – a region of icy objects beyond Neptune. It was more massive than Pluto and left astronomers with a dilemma, whether to add it and other larger bodies, to the list of planets, or to strip Pluto of its 75-year status as the ninth planet.

Mike Brown spoke to Witness History about his discovery and the public outcry that followed.

Photo: Professor Mike Brown (Getty Images)